Rotary drier, kiln, and the like



Sept. 29, 1953 G. BOJNER 2,653,393

ROTARY DRIER, KILN AND THE LIKE Filed Dec. 12, 1950 Patented Sept. 29, 1953 UNITED F F ICE Gustav- Bojner, Stockholm, I Sweden Application December 12; 1950, Serial No; 200,347 In Sweden September'l', 1950 Thisinvention relates to rotary: driers' or kilns forzdrying or other heatitreatment of granular oripul verulentor similar materials;

In my copending application Serial .No. 131,217 filed December 5, 1949; Izhave described-arr improvement of such rotary driers or kilns, in which airotary drum contains an inset or cage formed ofisubstantially radial partitions dividingtheinterior' of" the. drum: into longitudinal channels through-which the goods to be driedandfa dryingrsgas-pass indirect contact with each other; the materialbeing' advanced through the channels while performing a revolving. movement therein. According to the invention as illustrated in :saidcopending. application, alternate partitions have differentradial length, the long partitions serving chiefly: to catch the goods when moving upwards, whereas the short partitions allovw a: communication between adjacent channels; and'the innerends' of each long partitionand the next short-partition inirontiof said long partition =a-re interconnected'b'y means of closed wall elements. Essentially on account of the fact that the.- channels formedbetween-said two parti tions: are: closed towards the centreof the drum, 21051884800118 side-of the partitions will remain substantially free fromamaterial and thusan improvedsupplyof heat from th'e drying gas to the partitions as well as to the materialadhering: to the opposite side will beobtained.

An object of the" present invention :is to create astill further: improvement of apparatus of the type set forth above,.especiallyinconnection with the treatment ofrmateria-l of sticky nature; by

the-provision of "a strip extendinghelicall-y around the cage at the outer edgesof thelong partitions. Snclna. feed screw-does cause not only a positive advance. of the material through the drum'but also an increasezof the elfectiveheat transfer area as-the front sideof the feed screw contacts the materialxto .be; dried-while beingzcooled, whereas thEiTSCIEWW on;the-;freecpath above the levellorsthe material is. heated: by the drying gas: Moreover; the screwwill'preventzthe sticky. material-thorn remaining on the mantle surface of the drum and will; also impart: aturbu-lent movement; to the gas'sthusreducing the lamina flow of the. gas.v

Anotherobject of the: invention is'to create an improvement of. apparatus of? the type seti forth above by the: provisionof recesses in the. outer edgesxofthelonger partitions, said striprextend-f ing through said recesses. By aproper selection offthe longitudinal. extent: of said recesses the amountzof material fed by the screw can be adinstead; in. relationatoather amount of material caughtfby-theflongerpartitions;

Afurther object of theinvention is to create animprovement of apparatusofthe typeset forth above" by avoiding. central tubes or similar elements and providing-gutters spaced apart so as to leave :fr'ee spaces between themselves'both at the center and in the peripheral direction, said gutters being' mounted so as to present their rounded closed bottom portions'towardsthe center of the drum and their open-sides towards the .circum ference of the drum. Such freely spacedigutters allow afree flowing-of'the gas around'the feed screw and thechan-nel system, thus an: improved drying elTect. Moreover, thecostsof manufacturing the cage are reduced and corners are avoided :inwhich the material to be' dried :could stick.

According toanotherr-feature of this invention astrip is provided-; extending: helically; around the cage through recesses madein the edges of the: partitions.

Some embodiments of theinvention are byway oijexample illustratedin the accompanying, drawing, inwhich Fig; 1 is a longitudinal central section of a rotary'drier or" kiln, inwhich three-'difierent embodiments of cages according 1 to the-invention are shown, the left portion of ,Fig; 1 beingasection on the linela.la; of Fig. 2, theintermediate portion .of Fig. 1 being a section on the line. Ib-Ib ofFig; 3,= and-the right portion of Fig, 1 being a section on the line |c-Ic of Fig; 4;

Fig; Z.TlS-- across-section on the line 22 of Fig; 1;

Fig. 3 is a cross-section onthe' line 33 of Fig; 1;

Fig: 4 is a cross-section .on the line 4-4. of Fig. 1.

Referring now to the drawing, the drum- I which is rotatably journalled on rollers 2, is provided-at one end with asta-tionary chamber 3 having'an inlet chute-4-for the moist goods to be treated andan outlet- 5: for. the drying; gas, and at theiother end. with astationary chamber-6 havingan outlet 1 for the driedmaterialand an inlet 8.-for-hot drying-gas; In thedrum I. three somewhatdifferent inset bodies or'cagesE, F; G are shown; all of said cages being loosely-mounted in the drum so that they can rotate or roll within the: drum when the-latter rotates, while. suitable guiding means (not shown) in the drum prevent them from moving axially.

The-cage E, shownin cross-sectionin Fig. 2 is'composed ofa central core IZ. preferably made as atube and; the radial "partitions lfldand Ila, extending from said core.. The partitions Illa have a radial length greater than the. radial length of the partitions Ha but less than the difference between the radii of the drum and the core. Thus, the cage will obtain a somewhat eccentric position in the drum when resting against the lower portion of the mantle, for instance with two of its partitions lfia as shown in Fig. 2. The partitions lfla, and I la, divide the interior of the drum into longitudinal substantially sector-shaped channels A and B, and the partitions Ila should be of such a short length that they do not catch the material to be dried when the drum is charged to a normal height. Around the cage a strip we of sheet material or the like extends helically at a suitable pitch, said strip forming a feed screw for accelerating the advancing movement of the material through the drum in such cases in which the inclination or rotational speed of the drum is not sufficient or the properties of the material to be dried are such that an additional advancing force is required. The intermediate cage F, shown in crosssection in Fig. 3, comprises longitudinally extending gutters liib, Nb of curved sheet material or the like, the two walls Itb and lib of each gutter terminating at different distances from the mantle of the drum and, thus, corresponding to the partitions lea and I la, respectively, of Fig. 2. The gutters are joined together by means of strut-like members l2b so as to constitute a structural unit, no central core being provided. The third cage G, shown in cross-section in Fig. 4, is similar to the cage F, thus comprising gutters I00, I la joined together by the members l2c, but combined with a feed screw 13a of the same type as in Fig. 2.

In operation the three cages E, F, G will act substantially in the same manner. When the drum is rotating the material supplied is caught by the partitions Illa, lllb, lflc, respectively, and is advanced chiefly through the channels A while performing a rolling movement, thereby being dried by the drying gases flowing through the drum. As according to my said prior application substantially only one side of the partitions will be covered by the material, viz. the side of the long partitions facing forwards in the direction of rotation, and the side of the short partitions facing rearwards in the direction of rotation, whereas the opposite side will remain substantially free from the material and will be able to receive heat from the drying gases flowing in direct contact with said last-mentioned side, so that the partitions are effectively heated and a rapid drying of the boundary layer of any material adhering to the partitions is produced, thus causing the latter to loosen.

when the cage is combined with a feed screw, as are the cages E and G, each longer partition Illa or 0, respectively, should be provided with recesses 14 for each convolution of the strip l3a or I30 forming the feed screw, each such recess extending forwards in the direction of advance through the drum and having its axial extension selected according to the kind of material to be dried. Thus, according to the size of said recesses a different amount of material to be dried is fed by the feed screw, while the remaining part of the material is caught by the longer partitions. Irrespective of the proportions of the amounts fed by the screw and caught by the partitions, respectively, mixing of the materials is apparently effected when the materials fall from the partitions onto the lower portion of the mantle of the drum, whereby a uniform drying action is obtained.

The cages E, F, G are caused to rotate together with the drum by their friction against the inner surface of the mantle or by means of suitable tappets (not shown) and perform a slow stepwise rotation in the drum, whereby the loosening of any material adhering to the partitions of the cage is accelerated. The longer partitions impact against the inner surface of the mantle and strike said surface along axial lines of contact, whereby also any material adhering to the mantle is loosened. As the cages have a diameter of rolling smaller than the diameter of the mantle, the cages will evidently rotate or roll somewhat more than one revolution while the drum performs one revolution.

The provision of several different cages in the drum as shown in the drawing, is not essential to the invention inasmuch as the drum may be provided with two or more cages of the same structure or with one single cage extending substantially along the whole length of the drum. Moreover, the constructional details in carrying out the invention may be varied without departing from the scope of the invention.

The cages according to the invention may be mounted in already existing driers or rotary kilns and may be applied also to rotary kilns for burning cement or lime, a cage according to the invention then being provided in the inlet end of the kiln tube, and the sector system preferably being made of fire-proof sheet metal or other refractory material.

What I claim is:

1. An apparatus for the treatment of pulverulent materials to be dried, comprising, in combination, a drum rotatable in a predetermined direction, a cage mounted in said drum and including substantially radial partions of alternately different lengths in the radial direction, dividing the interior of the drum into longitudinal channels for the passage of material to be dried and of a drying gas in direct contact with each other, the space between each long partition and the next short partition in the direction of rotation being closed towards the center, and. a single strip extending helically around the cage at the outer edges of the long partitions for rotation together with the cage.

2. An apparatus for the treatment of pulverulent materials to be dried, comprising, in combination, a drum rotatable in a predeterined direction, a cage loosely mounted in said drum in an eccentric position and including substantially radial partitions of alternately different lengths in the radial direction, dividing the interior of the drum into longitudinal channels for the passage of the material to be dried and of a drying gas in direct contact with each other, the space between each long partition and the next short partition in the direction of rotation being closed towards the center, and a single strip extending helically around the cage at the outer edges of the long partitions for rotation together with the cage.

3. An apparatus for the treatment of pulverulent materials to be dried, comprising, in combination, a cylindrical drum rotatable in a predetermined direction, a cage mounted in said drum and consisting of substantially radial partitions of alternately different lengths in the radial directions, dividing the interior of the drum in longitudinal channels for the passage of material to be dried and of a drying gas in direct contact with each other, the space between each long partition and the next short partition in s tsee the direction of' rotation being closed towards the-"centen-recesses being provided in the-outer -edg-es'of sai'd longpartitions, and single strip extendinghelically aroundthe cage through said difierent lengths in the radial direction, dividing the interiorof the drum in longitudinal channels for the passage" of materialto be dried-and of a dryinggas in direct contact with each'other, the space between each longpartition and the 'next'shortpartition in the direction of rotation being closed towards the center, recesses being provided in the, outer edges-ofsaid long partitions, and a single strip extending helically around'the cage through said recesses for rotation together with the cage and passing aquantity of the pulverulent material through said recesses.

5. An apparatus for the treatment of pulverulent materials to be dried, comprising, in combination, a cylindrical drum rotatable in a predetermined direction, a cage mounted in said drum, including a plurality of longitudinally extending gutters having closed bottom portions and mounted so as to present their closed bottom portions towards the center of the drum and their open sides towards the circumference of the drum, said gutters being spaced apart. so as to leave free spaces between themselves extending from the center to the circumference of the drum and dividing the interior of the drum in longitudinal channels for the passage of material to be dried and of a drying gas in direct contact with each other, each gutter having its rear wall in the direction of rotation extending over a greater radial length than its front wall, and a strip extending helically around the cage for rotation together with the same.

6. An apparatus for the treatment of pulverulent materials to be dried, comprising, in combination, a cylindrical drum rotatable in a predetermined direction, a cage loosely mounted in said drum in an eccentric position and including a plurality of longitudinally extending gutters having closed bottom portions and mounted so as to present their closed bottom portions towards the center of the drum and their open sides towards the circumference of the drum, said gutters being spaced apart so as to leave free spaces between themselves extending from the center to the circumference of the drum and dividing the interior of the drum in longitudinal channels for the passage of material to be dried and of a drying gas in direct contact with each other, each gutter having its rear wall in the direction of rotation extending over a greater radial length than its front wall, and a strip extending helically around the cage for rotation together with the same.

'7. An apparatus for the treatment of pulverulent materials to be dried, comprising, in combination, a drum rotatable in a predetermined, direction, a cage mounted in said drum and including a plurality of longitudinally extending gutters having closed bottom portions and mounted so as to present their closed bottom portions towards the center of the drum and their open sides towards the circumference of the drum, said gutters 6 being spaced apart so as to leave'free spaces between-themselves extending fromthe center to the circumference of the drum and dividing the interior of the drum in longitudinal channel's forthe passage of material to be dried and ofa drying gas indirect contact with each other, each gutter havingits rearwall in the direction: of rotation extending over a greater radial length than its front wall, recesses being provided in the outer-edges ofsaidarear walls, and'azstriplextending helically around-the, cage for rotation together withthe same, and passing-a quantity of: the pulverulent-material throughisaidrecesses.

8. An apparatus for the treatmentofpulverulent: materials, comprising, in combination, a cylindrical drum rotatable in a predetermined direction, a cage loosely mounted in said:drum in 'an eccentric position and includinga plurality of longitudinally extending gutters having rounded closed "bottom portions and mountedzso as to: present: their: closed bottom portions to:- wards the center of the drumand their sides towards. the; circumference of the drum, said gutters being spaced apart so as to leavei-lfree spaces between themselves extending from, the center to the circumference of the drumxand dividing the interior ot the drum in longitudinal channels for the passage of material to be dried and of a drying gas in direct contact with each other, each gutter having its rear Wall in the direction of rotation extending over a greater radial length than its front wall, recesses being provided in the outer edges of said rear walls, and a strip extending helically around the cage for rotation together with the same, and passing a quantity of the pulverulent material through said recesses.

9. An apparatus for the treatment of pulverulent materials to be dried, comprising, in combination, a cylindrical drum rotatable in a predetermined direction, a cage mounted in said drum and including a plurality of longitudinally extending gutters having rounded closed bottom portions and mounted so as to present their closed bottom portions towards the center of the drum and their open sides towards the circumferences of the drum, said gutters being spaced apart so as to leave free spaces between themselves extending from the center to the circumference of the drum and dividing the interior of the drum in longitudinal channels for the passage of material to be dried and of a drying gas in direct contact with each other, each gutter having its rear Wall in the direction of rotation extending over a greater radial length than its front wall.

10. An apparatus for the treatment of pulverulent materials to be dried, comprising, in com bination, a cylindrical drum rotatable in a predetermined direction, a cage loosely mounted in said drum in an eccentric position and including a plurality of longitudinally extending gutters having rounded closed bottom portions and mounted so as to present their closed bottom portions towards the center of the drum and their open sides towards the circumference to the drum, said gutters being spaced apart so as to leave free spaces between themselves extending from the center to the circumference of the drum and dividing the interior of the drum in longitudinal channels for the passage of the material to be dried and of a drying gas in direct contact with each other, each gutter having its rear wall in the direction of rotation extending over a greater radial length than its front wall.

11. An apparatus for drying sticky materials with hot gases, comprising, a substantially cy1in drical drum rotatable in a predetermined direcfaces towards the circumference of the drum,

each gutter having its rear wall in the direction of rotation extending over a greater radial length than does its front wall, thereby permitting the sticky materials to get in contact only with the concave surfaces of the gutters and the hot gas to flow around both sides of the gutters, each long wall of the gutters having recesses in the outer edges, and a single strip secured to said unit and extending helically around said unit through said recesses for rotation together with said unit and moving a quantity of sticky material forward in proportion to the size of said recesses.

12. An apparatus for drying sticky materials by hot gases, comprising, in combination, a substantially horizontal rotatable drum for feeding the sticky material and the hot gases in one longitudinal direction through the same, and a loosely rolling unit in said drum, comprising a helically wound metal strip, only the feeding surface of the strip being in contact with the sticky material when passing through the lower portion of the revolution, and the entire strip surface being in contact with the gas when passing through the upper portion of the revolution.

GUSTAV BOJ N ER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,503,193 Lindhard July 29, 1924 1,959,772 Stalhane et a1 May 22, 1934 1,979,602 Bojner Nov. 6, 1934 2,102,054 Billings et a1. Dec. 14, 1937 2,422,939 Skoog June 24, 1937 FOREIGN PATENTS Number Country Date 201,966 Great Britain Aug. 3, 1923 441,326 Great Britain Jan. 17, 1936 387,684 Germany Jan. 5, 1924: 

